Hornbeck is once again mocking the belief's of Rachel and the people of Hillsboro through these lines. He refers to the serpent, an apple, Eva(Eve) and the Tree of Knowledge which are all in the bibical story of Adam and Eve. When the apple is eaten in the Adam and Eve story, the humans break God's rule, and humans are now given orginial sin, which is bad. Then Hornbeck states to Rachel that she won't find any Trees of Knowledge in her town, but you will find a few ignorant bushes. The ignorant bushes are the people who go against the beliefs of the people of Hillsboro; he implies that the people of Hillsboro aren't correct with their radical beliefs and ways.